Conventionally, a throw-away cutting tool with a cutting insert attached to a holder is used for a cutting tool for use in cutting process. Such a cutting insert used for this cutting tool is generally configured to include an upper surface, a lower surface and a side surface, and a cutting edge is formed at an intersecting portion between the upper surface and the side surface. By bringing the cutting edge into contact with a rotating workpiece such as a metal member, it is possible to cut a workpiece.
A configuration of a cutting insert is proposed such that projections to be in contact with chips of a workpiece are provided on an upper surface thereof in the same manner as cutting chips disclosed in Patent Document 1. The cutting insert disclosed in Patent Document 1 can curve a chip by placing the chip of a workpiece in contact with a first projection (first ridge) and a second projection (second ridge) extending from the first projection.
The cutting insert disclosed in Patent Document 1 first contacts with the chip in the second projection upon high depth cut process. Further, after getting on the second projection, the chip contacts the first projection. At this time, an upper end of the second projection is positioned in contact with the first projection. Thus, when moving from the top of the second projection to the top of the first projection, the chip smoothly moves. Therefore, curving the chip in an adequate shape is likely to be difficult. In such a case, it is likely that the chip is insufficiently curved and the chip becomes long more than necessary.
Patent Document 1: Japanese Patent Laid-open Publication No. 2009-208216